Economic analysis of natural resource and environmental issues inappropriately places too much emphasis on Pigouvian externalities and too little on Coasean property rights and transaction costs. The crucial questions are who has what property rights and what are the transaction costs associated with these property rights. Asserting an externality implicitly assumes a set of property rights and hence a distribution of the social costs, but it is precisely a lack of property rights that allows decision makers to ignore social costs. By viewing natural resource and environmental problems through a Coasean lens, we better focus our attention on how property rights evolve, how they influence transaction costs, and how those transaction costs affect the potential for bargaining to minimise social costs.